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61.
Nasim Ahmed Syed Alwee Aljunid R. Badlishah Ahmad Hilal A. Fadhil Mohd Abdur Rashid 《Optical Review》2012,19(1):1-6
The bit-error rate (BER) performance of the spectral amplitude coding-optical code division multiple access (SACOCDMA) system
has been investigated by using NAND subtraction detection technique with enhanced double weight (EDW) code. The EDW code is
the enhanced version of double weight (DW) code family where the code weight is any odd number and greater than one with ideal
cross-correlation. In order to evaluate the performance of the system, we used mathematical analysis extensively along with
the simulation experiment. The evaluation results obtained using the NAND subtraction detection technique was compared with
those obtained using the complementary detection technique for the same number of active users. The comparison results revealed
that the BER performance of the system using NAND subtraction detection technique has greatly been improved as compared to
the complementary technique. 相似文献
62.
JL García Ruano E Torrente A Parra J Alemán AM Martín-Castro 《The Journal of organic chemistry》2012,77(15):6583-6599
In this work, we report the use of the asymmetric intramolecular Pauson-Khand reactions of 4-aryl-4-cyano-1,6-enynes for obtaining enantiomerically enriched bicyclo[3.3.0]octenones, and the influence of both the quaternary stereocenter and the sulfur functions located at ortho-position of the aryl group, on their stereoselectivity and reactivity. The sulfenyl derivatives bearing substituted or unsubstituted triple bonds and mono- and disubstituted alkene moieties afford bicyclo[3.3.0]octenones in high yields with complete diastereocontrol. These results are explained by assuming the association of the lone electron pair at sulfur to the Co-alkyne complexes. 相似文献
63.
Nerea Ruiz del Árbol Carlos Sánchez-Sánchez Gonzalo Otero-Irurueta José I. Martínez Pedro L. de Andrés Ana C. Gómez-Herrero Pablo Merino Marten Piantek David Serrate Paolo Lacovig Silvano Lizzit José Alemán Gary J. Ellis María F. López José A. Martín-Gago 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23420-23427
On-surface synthesis is emerging as a highly rational bottom-up methodology for the synthesis of molecular structures that are unattainable or complex to obtain by wet chemistry. Here, oligomers of meta-polyaniline, a known ferromagnetic polymer, were synthesized from para-aminophenol building-blocks via an unexpected and highly specific on-surface formal 1,4 Michael-type addition at the meta position, driven by the reduction of the aminophenol molecule. We rationalize this dehydrogenation and coupling reaction mechanism with a combination of in situ scanning tunneling and non-contact atomic force microscopies, high-resolution synchrotron-based X-ray photoemission spectroscopy and first-principles calculations. This study demonstrates the capability of surfaces to selectively modify local molecular conditions to redirect well-established synthetic routes, such as Michael coupling, towards the rational synthesis of new covalent nanostructures. 相似文献
64.
Nasim Najjarzadeh Leonidas Matsakas Ulrika Rova Paul Christakopoulos 《Molecules (Basel, Switzerland)》2020,25(24)
Xylan is one of the most abundant carbohydrates on Earth. Complete degradation of xylan is achieved by the collaborative action of endo-β-1,4-xylanases and β-d-xylosidases and a number of accessories enzymes. In filamentous fungi, the xylanolytic system is controlled through induction and repression. However, the exact mechanism remains unclear. Substrates containing xylan promote the induction of xylanases, which release xylooligosaccharides. These, in turn, induce expression of xylanase-encoding genes. Here, we aimed to determine which xylan degradation products acted as inducers, and whether the size of the released oligomer correlated with its induction strength. To this end, we compared xylanase production by different inducers, such as sophorose, lactose, cellooligosaccharides, and xylooligosaccharides in Fusarium oxysporum f. sp. lycopersici. Results indicate that xylooligosaccharides are more effective than other substrates at inducing endoxylanase and β-xylosidases. Moreover, we report a correlation between the degree of xylooligosaccharide polymerization and induction efficiency of each enzyme. Specifically, xylotetraose is the best inducer of endoxylanase, xylohexaose of extracellular β-xylosidase, and xylobiose of cell-bound β-xylosidase. 相似文献
65.
Abdolghafar Abolhosseini Shahrnoy Ali Reza Mahjoub Sudabeh Shokrollahi Nasim Ezzati Kristiane Elsner Christoph T. Koch 《应用有机金属化学》2020,34(7):e5645
In this study, a step-by-step method for the synthesis of platinum nanoparticles and copper(I) complex supported on mesoporous silica hollow spheres (Pt-MSHSs-Cu) is introduced. Scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption, energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, and elemental and thermogravimetric analyses were applied for characterization of the surface, structure, size, phase composition, and morphology of the synthesized materials. The characterized material, Pt-MSHSs-Cu, was used as an efficient and heterogeneous catalyst in the Sonogashira coupling reaction under different reaction conditions. In comparison with MSHSs, Cu(I)-functionalized MSHSs (MSHSs-Cu), and Pt-MSHSs samples, the Pt-MSHSs-Cu catalyst exhibited significantly increased catalytic performance with 91.50% yield. Therefore, the results obtained suggested a synergistic effect derived from platinum nanoparticles, MSHSs substrate, and copper(I) complex, which enhanced the rate of the Sonogashira coupling reaction. 相似文献
66.
Juan Carlos Ahumada Juan Pablo Soto Carlos Alemán Juan Torras 《Journal of polymer science. Part A, Polymer chemistry》2021,59(24):3167-3180
Conducting polymer synthesis of a new benzobisoxazole/thiophene derivative is reported. The conjugated co-polymer presents the lowest bandgap (1.78 eV) reported for a neutral benzobisoxazole/thiophene polymer. Electrochemical polymerization is carried out by cyclic voltammetry, and the new conducting polymer is characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the coupling of the monomer unit occurs at the 2,2′ positions of the thiophene ring. Theoretical studies in derivatives of this family of compounds are conducted to validate the effect on the bandgap modulation due to the change in the substituent on the phenyl moiety of the monomer. The comparison between experimental and theoretical properties shows the substituents impact on the optical properties of the system, and its viability to be used in sensors. 相似文献
67.
Summary In order to get insight into the conditions that make polyglycine (PG)II a stable structure, the conformational features of three model molecules closely related to the PGII conformation were investigated. The model molecules selected were glycine dipeptide (AGN), glycine tripeptide (AGGN), and glycine tetrapeptide (AGGGN). Environmental effects were mimicked by means of formaldehyde molecules. The calculations were carried out at the SCF semiempirical level, using the AM1 method. The calculations show that of the three systems considered, only the AGGGN molecule presents a minimum energy conformation which corresponds to a PGII structure. The environmental conditions in which this conformation is found were also analyzed. 相似文献
68.
A concise high-yielding route to synthetically useful 1,2-diaryl (and 1-alkyl-2-aryl) ethyl and propylamines in high enantiomeric purity is described. The key step of this route is the completely stereoselective addition of lithium (R)-ortho-(p-toluenesulfinyl)benzylic carbanions to (S)-N-p-toluenesulfinylimines, which takes place in very high or quantitative yields. N-Desulfinylation and C-desulfinylation of the resulting adducts can be achieved with no loss of optical purity employing conventional methods (TFA and Raney-Ni, respectively). 相似文献
69.
Ding T Alemán EA Modarelli DA Ziegler CJ 《The journal of physical chemistry. A》2005,109(33):7411-7417
Four free-base corroles with electron-donating or electron-withdrawing groups on the para or 2 through 6-positons of the meso phenyl rings were prepared via either Paolesse or Gross conditions and investigated for their absorption and emission properties. The triaryl corroles 5,10,15-triphenylcorrole, 5,10,15-tris(pentafluorophenyl)corrole, 5,10,15-tris(p-nitrophenyl)corrole, and 5,10,15-tris(p-methoxyphenyl)corrole were examined. Absorption, steady-state, and time-resolved fluorescence measurements were performed on all compounds in both nonpolar (dichloromethane) and polar (dimethylacetamide) solvents. The experimental evidence points to hydrogen bonding with an internal N-H group as the most likely factor in the solvent-dependent photophysical behavior of these corroles, that is also highly dependent upon substitution. 相似文献
70.
Farzin Marandi Dr. Nasim Asghari Massomeh Gorbanloo Ali A. Soudi Peter Mayer 《无机化学与普通化学杂志》2007,633(4):536-538
[Pb(trz)(tfpb)(H2O)] ( 1 ) (trz and tfpb are the abbreviations of 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine and 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butandionate, respectively) have been synthesized and characterized by elemental analysis and IR, 1H NMR, spectroscopy. The single‐crystal structure of 1 shows the coordination number of the Pb2+ ions is eight with three N‐donor atoms from a “trz” ligand and four O‐donors from the dionate ligand and one molecule of water. The supramolecular features in this complex are guided by lone pair activity and control of strong hydrogen bonds, weak directional intermolecular interactions and aromatic π‐π stacking interactions. 相似文献